to spawn an external process and get its output. Only implemented for
   UNIX-style systems at present.
 * src/misc/httpd.c: New "handler" node type which bypasses the internal
   HTTPD behaviour.
 * modules/control/http: New --http-handlers option to dedicate
   particular extensions to external programs (PHP or Perl for instance).
   This is in accordance with the CGI/1.1 specification.